The present invention is directed to bicycle transmissions and, more particularly, to bicycle transmissions internally mounted within a wheel hub.
JP 5-65094 discloses an internally mounted bicycle transmission that includes a hub axle, a drive member rotatably mounted around the hub axle, a hub body rotatably mounted around the hub axle, and a gear mechanism coupled between the drive member and the hub body for communicating rotational force from the drive member to the hub body through multiple transmission paths. The gear mechanism includes a sun gear rotatably supported around the hub axle, a planet gear supported by a planet gear carrier for rotation around the hub axle, and a ring gear engaging the planet gear. A first one-way clutch is coupled between the drive member and the ring gear, and a second one-way clutch is coupled between the drive member and the planet gear carrier. Various transmission paths may be selected by selectively engaging and disengaging the first or second one-way clutches, thus resulting in multiple speed stages having relatively narrow steps between adjacent speed stages.
With an internally mounted transmission as described above, the ring gear and the driver must be molded and assembled separately, which drives up the cost and makes the structure more complicated. Furthermore, it is necessary to use a clutch mechanism that links the ring gear and the driver, thus further increasing the cost and making the structure more complicated. When there are more parts involved, there also is the risk that there would be looseness caused by manufacturing error or the like between the driver and the ring gear.